A variety of control strategies have been developed to decrease the fuel consumption within an internal combustion engine. One type of control strategy may include temporarily shutting down operation of an internal combustion engine during idle-stops and quickly restarting the engine, when needed, in an attempt to decrease fuel consumption and well as emissions from the vehicle. In one example, a direct-start (DS) control strategy may be used when restarting the engine from idle-stop conditions, where a first combustion event of the start occurs while the engine is still at rest, with or without starter motor assistance. Vehicles utilizing DS may shut down operation while a vehicle is stopped from an idle condition via the discontinuation of fuel injection, valve actuation, and/or spark discharge within the combustion chambers. Subsequent to engine shut-down, fuel may be injected into to a selected combustion chamber and ignited via a spark discharge to quickly and seamlessly re-start combustion within the engine, in an attempt to reduce fuel consumption as well as emissions during start-up.
However, the Applicants have recognized that vehicles utilizing DS may experience misfires, variable torque output, and in some cases increased emissions during DS operation, due to the variable and unpredictable position of the piston as well as the improperly mixed air and fuel and the motion of the ignitable mixture within the combustion chamber. In particular, the position of the first piston selected for DS from rest may be proximate to the top dead center (TDC) of the combustion chamber, which may in turn lead to an inconsistent mixing of the air and fuel and incomplete combustion. The incomplete and inefficient combustion may cause the aforementioned problems (e.g. misfires and variable torque output). Furthermore, the noise, harshness, and vibration (NVH) within the vehicle may be exacerbated due to the variable torque output, decreasing customer satisfaction.
A method for operation of a vehicle having an internal combustion engine is provided. The internal combustion engine may include one or more combustion chambers, a fuel delivery system including a direct fuel injector coupled to each combustion chamber, an ignition system including one or more spark plugs coupled to each combustion chamber, a piston disposed within each combustion chamber, and an intake and an exhaust valve coupled to each combustion chamber, the internal combustion engine providing motive power to the vehicle. The method may include discontinuing combustion operation within the internal combustion engine responsive to idle-stop operation. The method may further include, during a direct-start, performing multi-strike ignition operation per combustion cycle via one or more selected spark plug(s) for at least a first combustion cycle in a combustion chamber following the discontinuation of combustion operation, the one or more selected spark plug(s) coupled to the combustion chamber.
In this way, emissions and variable torque output during DS may be reduced and in some examples prevented, due to the increased combustion stability of a multi-strike ignition operation.
Another method of operation of a vehicle having an internal combustion engine is provided, in other examples. The method may include, during a first start, when a duration following idle-stop operation is below a threshold value, directly starting the engine from rest with a first combustion event including multi-strike ignition operation per combustion event, where a first amount of starter motor assistance to the engine is provided. The method may further include during a second start, when the temperature of the engine is below a threshold value and/or an operator initiated ignition signal has been received via the vehicle, starting the engine from rest with a second combustion event including only a single strike ignition operation per combustion event, where a second amount of starter motor assistance to the engine is provided, the second of starter motor assistance greater than the first amount of starter motor assistance.
In this way, during a direct start when the starter is used to a lesser extent, or not at all, additional current from the vehicle electrical storage (e.g., battery) is available for the multi-strike operation. However, when additional energy is needed to power the increased starter assistance, less current from the vehicle electrical storage (e.g., battery) is needed for the single strike ignition. In this way, it is possible to balance current draw during starts, while at the same time take advantage of the increased current availability of direct starts to enable multi-strike ignition operation. Likewise, when additional starter motor assistance is used, less current is used for single-strike ignition.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.